1. Field of the Invention
This invention relates to surgical biopsy needle instruments. More particularly, this invention relates to an interlocking handle arrangement for a coaxial bone marrow biopsy needle assembly.
2. State of the Art
Known biopsy needles generally include a cannula having a lumen extending therethrough, and a trocar or stylet which is removably inserted through the lumen of the cannula. The proximal ends of the cannula and trocar are provided with some type of gripping means and the distal ends of the cannula and trocar are sharpened to a bone piercing edge. In order to obtain a bone marrow specimen, the trocar and cannula are forced through the outer hard layer of the bone containing the marrow. Once the softer, internal region of the bone is reached, the trocar is withdrawn. A specimen is obtained either by advancing the cannula further into the bone to obtain a core sample, or by coupling a fluid conduit to the proximal end of the cannula and aspirating a liquid sample. When taking a core sample, the cannula containing the core sample of bone marrow is carefully withdrawn so as to retain the marrow material.
The bone marrow biopsy procedure is quite painful to the patient and requires much exertion by the physician. Early problems with biopsy needles involved the sharpness of the cannula and trocar and the gripping means used so that the needle could be placed accurately and the bone could be penetrated quickly. U.S. Pat. No. 4,356,828, for example, discloses an improved finger gripping member and U.S. Pat. No. 4,403,617 discloses particular cutting edge configurations for the trocar and cannula.
Developments in the gripping means of the trocar and cannula continued with emphasis placed on the secure engagement of the trocar within the cannula and ease of use for the physician. U.S. Pat. Nos. 4,922,602 to Mehl, 4,838,282 to Strasser et al., 4,793,363 to Ausherman et al., and 4,469,109 to Mehl, for example, disclose fairly elaborate interlocking systems between the trocar gripping means and the cannula gripping means and different shapes for the gripping means. The object in providing an interlocking system between the trocar and the cannula is to keep the trocar securely in the cannula while the instrument is being forced through the outer hard layer of bone. Strasser et al. shows a frictional engagement between the trocar handle and the cannula handle. This type of interlocking system is often either too loose to hold the handles together securely or too tight to allow easy separation of the handles when removing the trocar from the cannula. Mehl and Ausherman et al. show a pin and groove twist-locking system. Here, the trocar handle is aligned with the cannula handle in a first position, pushed closer to the cannula handle and then twisted relative to the cannula handle to lock the handles to each other. This type of interlocking system is almost always secure but it is also almost always difficult to unlock the handles from one another.
The previously incorporated parent of the instant application discloses a three part bone marrow biopsy needle assembly for obtaining a bone marrow core biopsy and a bone marrow aspirate biopsy in a single procedure. The needle assembly has an outer aspiration sheath which closely surrounds a coaxial inner hollow coring needle, and a trocar which extends through the coring needle. A handle arrangement is provided to allow insertion into the bone of the central trocar, the core biopsy needle and the outer aspiration sheath as an assembly, and to further allow stable manipulation of each component of the system without displacing the outer aspiration sheath. The handle arrangement is provided with a latching mechanism which prevents the trocar and aspiration cannula from being assembled together by themselves. The coring needle must inserted into the aspiration cannula and the coring handle attached to the aspiration handle before the trocar handle can be attached. Interlocking of the three handles is accomplished by a biased radial locking pin in the handle of the outer aspiration sheath which engages a notch in longitudinal projections extending from the handles of the coring needle and the trocar. This interlocking system overcomes the disadvantages of the frictional engagement systems and the twist-lock systems. The handles are held securely together but are easily separated from each other by the physician.
It has been recognized that, while it is often necessary to take both solid and liquid biopsy samples from the same site, it is sometimes only necessary to take a solid or a liquid sample. In those cases, the three part bone marrow biopsy needle assembly of the parent application can be used, but requires the otherwise unnecessary inclusion of both the coring needle and aspiration sheath in the assembly prior to insertion into the bone marrow and the removal of both the trocar and the coring needle prior to aspiration.